Eradicating God's Fiery Serpents

Will Hamilton, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0SP

INTRODUCTION

According to The Old Testament (Numbers 21:4-9), God sent “fiery serpents” down to Earth as a punishment for the Israelites speaking ill of Moses and Himself as they wondered the desert. Its authors may have been referring to the parasitic nematode worm, Dracunculus medinensis, or Guinea worm [1].

Guinea worm has tormented our species for thousands of years, as evidenced by infected Egyptian mummies and writings from the Ancient Greeks [2]. The symbol of Western medicine, the Caduceus (right), may be inspired by the traditional treatment for dracunculiasis (also called Guinea Worm Disease, GWD): winding the worm up around a stick to pull it from its victim’s flesh [2].

The World Health Organization (WHO) believes we have passed the tipping point in the struggle to eradicate GWD forever [3]. There is good reason to hope that the disease will be eliminated within the working lifetime of current medical students. This would be a triumph of international development efforts, humanitarianism and global healthcare on a scale that has not been seen since the eradication of smallpox in 1979.

GUINEA WORM LIFE CYCLE AND DISEASE

Guinea worms have a very simple life cycle [4]. Live larvae are released from the adult female into water, where they infect small crustaceans called copepods. When humans drink water contaminated with infected copepods, the worms are released in the stomach and migrate out to the body cavity. After mating, the males die almost immediately, while the female migrates to superficial connective tissue in the lower limbs, particularly the feet. A vigorous host inflammatory response gives rise to the development of a blister which bursts exposing the anterior end of the worm. This is extremely painful and irritating for the skin, motivating the host to seek relief by submerging the afflicted limb into cool water. At this point, the first stage larvae are expelled from the blister and their ingestion by suitable copepods completes the life cycle. Evolution never fails to inspire awe through its simultaneously ingenious and horridly cruel works of nature [5].

The most serious risk in GWD is secondary bacterial infection at the female worm’s exit site, causing cellulitis or sepsis. The calcified remains of dead worms may cause long-lasting pain and, rarely, disfigurement of the leg. In addition to the dreadful reduction in quality of life for the individual, GWD has a significant negative impact on socioeconomic growth, both by immobilizing the workforce and by making it difficult for people to attend school.

ERADICATION EFFORTS AND PROGRESS

It should be very easy to eradicate Guinea worm due to its strictly waterborne transmission route and the fact that there are no known reservoir hosts. All that is needed to utterly break the nematode’s life cycle is clean drinking water for humans in endemic regions, so the infected copepods never become ingested. Eradication can take place without any ‘medical’ intervention at all. It is purely about improving drinking water and raising public awareness.

A major contributor to the global eradication campaign is the Carter Center, a not-for-profit organization founded by former U.S. president Jimmy Carter and his wife Rosalynn Carter. Along with the Center for Disease Control (CDC), UNICEF and the WHO, the campaign has focused on the following key areas since the 1980s [2]:

Educating the public and raising awareness, e.g. ensuring that people are aware of the importance of filtering their drinking water, and that infected individuals avoid public water sources.

Providing water filters capable of filtering out copepods.

Providing resources for digging wells to access underground water stores that are uncontaminated.

Monitoring populations for new outbreaks and organizing responses

This strategy has been immensely successful [7]. In 1986, when the Carter Center first became involved in the eradication programme, there were an estimated 3.5 million cases of GWD in over 20 endemic countries in Africa and Asia. The provisional figures for 2010 indicate that the incidence has dropped by >99% to 1,797 [6]; the disease is now endemic in only four countries: the Sudan, Ghana, Mali and Ethiopia [Fig. 1]. The success of the programme is testament to how much progress can be made in treating and preventing neglected tropical diseases provided the motivation and financial backing exists.

Figure 1. Reported incidence of Guinea Worm Disease 1989-2006

The road to eradication has not been without obstacles. Problems include a lack of political motivation in endemic countries, a bloody civil war in the Republic of Sudan, and a lack of monetary funding (as of 2007 the Guinea worm eradication programme had run on just US$225 million for its entire 20 year history [7]). The worm’s one-year incubation period in the human host also complicates matters, as monitoring must be thorough to avoid outbreaks occurring months after presumed ‘eradications’ [7].

A particularly heart-warming story from the eradication programme is the ‘Guinea worm ceasefire’ in the Sudan. The Sudanese civil war of 1983-2005, fought between the mainly Christian south and the mainly Muslim north, was the longest civil war in African history and resulted in the deaths of millions of people [8]. It consistently hampered humanitarian efforts as public health workers could not gain access to rural communities in the war-torn country. In 1995, a four-month ceasefire was negotiated principally by Jimmy Carter himself, which allowed the guinea worm eradication programme and the Sudan’s onchocerciasis control programme to finally make real progress [7]. (In 2002 Jimmy Carter became the only U.S. president to receive a Nobel Peace Prize for efforts made after their presidency).

The Guinea worm eradication programme received a huge financial boost in 2008 when a combination of the Carter Center, the Bill & Malinda Gates Foundation and the U.K. government pledged $55 million to help finance the end stages of eradication [9], and there is every indication that the efforts will be successful.

ETHICAL AND PHILOSOPHICAL CONSIDERATIONS

The only infectious diseases eliminated by medical science so far are smallpox and rinderpest (which affects domestic livestock). But these are both caused by viruses- barely considered “living” by most biologists. D. medinensis, in contrast, is a living multicellular animal that will be wiped off the face of the Earth, presumably forever. There is no doubt that this will make the world a better place. However, it does raise intriguing philosophical and moral questions. In the prevailing climate of promoting biodiversity and protecting endangered organisms, how do we decide which species are sufficiently bothersome to warrant destruction? And can we avoid knock-on effects in ecosystems that are both highly sensitive to interference and notoriously difficult to predict? What gives our species the right to make these decisions on behalf of the rest of the natural world? Dracunculiasis will hopefully be the first of many diseases to be eliminated in the 21st Century (other potential targets include polio, lymphatic filariasis and malaria), so it is likely that these questions will become increasingly relevant.

CONCLUDING REMARKS

Through the dedicated work of many organizations, most notably the Carter Center, we are on course to eliminate Guinea worm within the next few decades. This will save many millions from unnecessary suffering and pain, and promote economic growth by reducing the crippling burden of morbidity and disease. In my view, it is an example of what Abraham Lincoln called the “better angels of [human] nature”: intelligence, forethought and large-scale teamwork across diverse nationalities and cultural/ political boundaries, with the explicitly altruistic intention of improving quality of life for untold millions. The Bible asserts that these “fiery serpents” were a punishment from God. Regardless, they are a foe that Humanity will defeat on its own, united.